DNS client, OT?

[Chris Buxton]

That's not how it works. It's up to the resolver logic to determine  
how to use the DNS servers provided. Older OS's used them in order.  
Newer OS's do not.

The exact logic used is something I've debated with other sysadmins  
over recent years - my empirical evidence against their reading of the  
docs. It seems to me that at least some stub resolvers will use  
something analogous to RTT to pick a resolving name server;  
documentation apparently suggests that there is network topology  
optimization or simple cycling going on, depending on whether you're  
talking about Windows or the BIND stub resolver.

Chris Buxton
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On Feb 6, 2008, at 12:52 PM, david brett wrote:

> I just ran into an issue which caught me be surprised.  This may be  
> off topic?
>
> I have a DHCP server handing out three DNS, the third one is a  
> backup to the ISP DNS incase the
> internal ones go down the users could still get to the Internet.
>
> What happened is the client started randomly to use the third DNS  
> (ISP DNS) when looking up names!
> The first two DNS were reachable and running.  This goes against the  
> way I understood it to work.
> I thought it would use the DNS in order and only if the first one  
> didn't respond.  Do I have it
> wrong or is something else going on here?
>
> david
>
> P.S. These are windows xp clients
>
>
>       
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